Another Confusing Drift Test Result

  • Creator
  • #36077

    Hey folks,

    I’ve looked through threads for similar questions and can’t find any, so here’s another question about a strange drift test result.

    I retested my AeT at 140 last week as my pace at my old AeT of 135 has increased by about a mile/minute on flat ground over the last couple of months. I warmed up for about 15 minutes, and my heart rate began to rise quickly after I started the test. My average HR in the first 15 minutes was 141, and in the second 15 minutes was 145. Extrapolating a trend from my first-half results would have yielded an average first-half HR of 144 and an average second-half HR of 152. This 8 bpm spread would have been just over a 5% drift rate. But instead my heart rate quickly dropped after I crossed the 30 minute mark, and I averaged 143 bpm in the second half of the test. This kind of peak-shaped HR graph for a test was pretty out of character for my norm. Does this just mean my AeT is now significantly above 140? It seems unlikely it’s much higher than that given where I was a few months ago.

    If the test got messed up, what could the culprit be? Maybe I didn’t warm up enough? My gym’s treadmills only go for 60 minutes before automatically cooling down, so I had a friend get another treadmill next to mine up to speed and incline halfway through, allowing me to jump to that treadmill with no break in the action and avoid a cooldown at the 45 minute mark. The second treadmill felt exactly the same, but maybe it was imperceptibly slower and that caused my HR to drop? I also noticed that my HR looks pretty jumpy in general, so I’m attaching pictures of the graphs from my first and second halves of the test. I don’t think it’s a faulty monitor- I was using a fairly new and well-cared for strap.

    Thanks for the help yall!

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  • Participant
    depeyster on #36082

    ThThis one has an an elementary solution. You didid not calibrate the speed or inclination ofof the two treadmills. Scott Semple has his owown blog with a great post on how to cacalibrate speed.I posted on this forum about the utility of using a phone ininclinometer app to measure real ininclination. Better to pause a miminute and restart the same treadmill between stages.

    Anonymous on #36106

    Distinguishing between 141, 145, and 143 is false precision. Heart rate isn’t that precise. I think it’s best to think of heart rate, not in single-digit BPM, but 5-BPM “buckets”.

    I think you should do another test with a target of 145 or 150, probably the latter. If the machines shut down at 60′, don’t split the test, just separate it from the warm-up. Warm up for 15-20′ to find the speed, and then reset the machine. Then hold the same speed on the same machine for the test. The time required to reset the machine won’t make a difference to the test.

    Also, your HR output looks really stochastic. That’s the typical output from wrist-based optical monitors (which are junk). If it’s a new, clean strap with a good, moist connection, I’m not sure why it would be that jagged.

    WillB on #36107

    Thanks for the advice on retesting at a higher BPM and on just resetting the treadmill after the warmup, that’s really helpful.

    And yeah it is really stochastic, which I think is characteristic for me. Sitting in my car driving to the trailhead this morning my watch was showing an HR reading that was bouncing around all the way between 52bpm and 60bpm. Any idea what that would mean if it’s actually me and not a bad strap/monitor?

    Anonymous on #36110

    At rest, variations between 52 and 60 sound about normal. But changes from low-130s to high 140s at a constant pace seem like a lot. Not sure!

    WillB on #37016

    I retested my AeT with a target of 140 and got a first half average of 143 and a second half average of 150, putting me at exactly 0.05. Can you take a look at the graph again and see it still looks unusually stochastic to you? I’m pretty sure that big spike to 167 was an HR monitor thing since it dropped back when I repositioned the strap, but even so there’s a lot of jumping.

    I also did this test after a big load week so it’s probably impacted by fatigue. Could I assume that my AeT is another 5 bpm higher (which also would make sense given my pace improvements and the low drift on my last test), or should I really just do another test when I’m rested?

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    Anonymous on #37037

    I see what’s happening now. I didn’t notice at first, but the graph minimum is 130. Because the graph is “zoomed in” the stochasticity will appear greater. If you could “zoom out”, then I bet this same HR output would appear more normal and less jagged.

    Anyway… I would do both. I think you could go ahead and use 140-145 as AeT HR, and then at the tail end of your next recovery week, do another drift test to confirm.

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